By Dan Proudman

8 February 2018 — 5:35pm

Even on the manicured lawns of high-society polo, these were prized ponies. Some were estimated to be worth well over $100,000 each and many belonged to members of the billion-dollar Kahlbetzer agribusiness empire.

Authorities are now scrambling to discover why 16 of these "A-grade" ponies, all reported to be in good health after competing on the Apple Isle, ended up "cold dead" only an hour after disembarking in Melbourne from the Spirit of Tasmania on January 29.

Adding to the mystery is the survival of a similar number of horses making the trip back to the mainland in a second horse trailer also being managed by the former Australian polo team captain and coach, Andrew Williams.

Mr Williams owned some of the dead animals and managed others belonging to his employer Johnny Kahlbetzer, the son of German-born agribusiness baron John Dieter Kahlbetzer, whose fortune was estimated by Forbes last year as $950 million.

Along with his younger brother, Mr Kahlbetzer runs the family's extensive agribusiness, property, venture capital and resources operations and owns Jemalong Polo Club at Forbes, where the dead horses were based.

Mr Williams, regarded as one of Australia's top players, who also owned some of the animals and was responsible for their welfare, said his career and livelihood were now on hold after finding all but two of them dead in the back of his horse trailer after arriving at a property at Yarra Glen, about 55 kilometres from Melbourne.

"It was my worst nightmare. Within an hour of leaving the boat, I had 16 horses that were cold dead and two fighting to survive," Mr Williams said in a statement.

Mr Williams, who owned and ran Willo Polo Club at Richmond north of Sydney before moving to Forbes to manage Jemalong Polo Club, said he "went into survival mode" to save the two remaining animals before driving the dead horses to Wagga for full autopsies.

Johnny Kahlbetzer, of the Twynam Agricultural Group, pictured in 2005. Mr Kahlbetzer owned some of the dead horses.

Photo: The Land/Rural Press

He said he had engaged lawyers and was seeking answers.

"I have lost a breeding line that was priceless to me, and I have already had to knock back playing commitments," he said.

Former Australia polo captain Andrew Williams (in white).

Photo: Stephen Mowbray

He said he had performed the trip 11 times before and had not seen any signs of distress as he loaded the two trailers onto the Spirit of Tasmania for the overnight trip to Melbourne, which can take up to 11 hours.

Tasmania had experienced a heatwave over the Australia Day long weekend, including a new highest minimum temperature for January in Hobart on the night of the voyage at 24 degrees.

"I didn't change anything. Yes, it was a warm night," he said in the statement.

"I have asked for answers, but have received nothing.

"What I know is I saw 18 healthy horses on my truck just before departure in Tasmania, and an hour after leaving the boat in Melbourne I discovered 16 of them were dead and cold.

"I am a farmer, a polo player and a breeder of ponies. They are the reason I can feed my family. To have that taken away is gut-wrenching.

"It is with the legal team now and hopefully they will receive the answers I deserve."

Representatives of the Spirit of Tasmania said the organisation would not comment while investigations continued.

A spokeswoman for Tasmania's Department of Primary Industries, Parks, Water and Environment, said the department was being assisted by other jurisdictions, including chief veterinary officers in Victoria and NSW.

"As per standard practice, no further details will be released as this is an ongoing investigation," the spokeswoman said.